Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens, and the like. Touch screens, in particular, are popular because of their ease and versatility of operation, as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus, or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch and the position of the touch on the touch sensor panel, and the computing system can then interpret the touch in accordance with the display appearing at the time of the touch and thereafter perform one or more actions based on the touch. In the case of some touch sensing systems, a physical touch on the display is not needed to detect a touch. For example, in some capacitive-type touch sensing systems (e.g., far field touch sensing systems), fringing electrical fields used to detect touch can extend beyond the surface of the display, and objects approaching near the surface may be detected near the surface without actually touching the surface.
Capacitive touch sensor panels can be formed by a matrix of substantially transparent or non-transparent conductive plates (e.g., touch electrodes) made of materials such as Indium Tin Oxide (ITO). In order to detect such changes, in some examples, the touch electrodes can be coupled to sense circuitry using substantially transparent or non-transparent sense connections (e.g., traces) that can be composed of any electrically conductive material, such as ITO. It is due in part to their substantial transparency that some capacitive touch sensor panels can be overlaid on a display to form a touch screen, as described above. Some touch screens can be formed by at least partially integrating touch sensing circuitry into a display pixel stackup (i.e., the stacked material layers forming the display pixels).
The touch electrodes can be varied in size and/or location to appropriately route the traces along the touch sensor panel to the sense circuitry. In some instances, the increased capacitive coupling of the larger-sized touch electrodes can affect the performance of the touch electrodes, thereby hindering touch sensitivity of the touch panel and limiting the speed at which the touch panel can operate.